1. Field of the Invention
The present invention relates to an apparatus and a method for driving a voice coil motor (VCM), and more particularly, to an apparatus and a method for driving a VCM used for various purposes, such as lens position control, or the like, in a camera having an automatic focus control function.
2. Description of the Related Art
As the use of portable wireless terminals has markedly increased in recent times, portable wireless terminals have had various functions added thereto, in addition to their original voice communications function. A camera module, one of various features added to portable wireless terminals, carries out automatic focusing by allowing a voice coil motor (VCM), provided in portable wireless terminals, to move a lens.
The voice coil motor (VCM) is developed by considering the fact that a speaker is vibrated back and forth by force generated according to Fleming's left hand rule between voice current flowing in a voice coil of the speaker and magnetic force generated by a permanent magnet. A DC motor or a stepping motor has rotary motion, whereas the voice coil motor (VCM) has linear reciprocating motion over a short distance and therefore may be used for automatic focus control.
Generally, in the case of portable wireless terminals that are required to be miniaturized, since a driving power supply does not supply negative (−) voltage, a method of allowing one side of a movement range of a lens to be set as an initial position and then applying DC current to a voice coil motor (VCM) to move the lens from the initial position may be used in the voice coil motor (VCM).
However, the foregoing method has limitations in that the distance of movement is increased, and thus a large amount of voltage is required in order to move the lens from the initial position to a set maximal magnification, and current consumption is thereby increased.